Alzheimer's Disease: Fatty Acids We Eat may be Linked to a Specific Protection via Low-dose Aspirin.
Pomponi Massimo F L,Gambassi Giovanni,Pomponi Massimiliano,Masullo Carlo
Aging and disease
It has been suggested that cognitive decline in aging is the consequence of a growing vulnerability to an asymptomatic state of neuroinflammation. Moreover, it is becoming more evident that inflammation occurs in the brain of Alzheimer's disease (AD) patients and that the classical mediators of inflammation, eicosanoids and cytokines, may contribute to the neurodegeneration. In agreement with this observation, aspirin (ASA) - a non-steroidal anti-inflammatory drug - may protect against AD and/or vascular dementia. However, both the time of prescription and the dose of ASA may be critical. A major indication for low-dose ASA is in combination with docosahexaenoic acid (DHA). DHA plays an essential role in neural function and its anti-inflammatory properties are associated with the well-known ability of this fatty acid to inhibit the production of various pro-inflammatory mediators, including eicosanoids and cytokines. Higher DHA intake is inversely correlated with relative risk of AD and DHA+ASA supplement may further decrease cognitive decline in healthy elderly adults. Although low-dose ASA may be insufficient for any anti-inflammatory action the concomitant presence of DHA favours a neuroprotective role for ASA. This depends on the allosteric effects of ASA on cyclooxygenase-2 and following production - from DHA - of specific lipid mediators (resolvins, protectins, and electrophilic oxo-derivatives). ASA and DHA might protect against AD, although controlled trials are warranted.
Diverse functional roles of reactive cysteines.
Pace Nicholas J,Weerapana Eranthie
ACS chemical biology
Cysteine residues on proteins play key roles in catalysis and regulation. These functional cysteines serve as active sites for nucleophilic and redox catalysis, sites of allosteric regulation, and metal-binding ligands on proteins from diverse classes including proteases, kinases, metabolic enzymes, and transcription factors. In this review, we focus on a few select examples that serve to highlight the multiple functions performed by cysteines, with an emphasis on cysteine-mediated protein activities implicated in cancer. The enhanced reactivity of functional cysteines renders them susceptible to modification by electrophilic species. Toward this end, we discuss recent advancements and future prospects for utilizing cysteine-reactive small molecules as drugs and imaging agents for the treatment and diagnosis of cancer.
Short-chain lipid peroxidation products form covalent adducts with pyruvate kinase and inhibit its activity in vitro and in breast cancer cells.
Sousa Bebiana C,Ahmed Tanzim,Dann William L,Ashman Jed,Guy Alexandre,Durand Thierry,Pitt Andrew R,Spickett Corinne M
Free radical biology & medicine
Pyruvate kinase catalyses the last step in glycolysis and has been suggested to contribute to the regulation of aerobic glycolysis in cancer cells. It can be inhibited by oxidation of cysteine residues in vitro and in vivo, which is relevant to the more pro-oxidant state in cancer and proliferating tissues. These conditions also favour lipid peroxidation and the formation of electrophilic fragmentation products, including short-chain aldehydes that can covalently modify proteins. However, as yet few studies have investigated their interactions with pyruvate kinase, so we investigated the effects of three different aldehydes, acrolein, malondialdehyde and 4-hydroxy-2(E)-hexenal (HHE), on the structure and activity of the enzyme. Analysis by LC-MS/MS showed unique modification profiles for each aldehyde, but Cys152, Cys423 and Cys474 were the residues most susceptible to electrophilic modification. Analysis of enzymatic activity under these conditions showed that acrolein was the strongest inhibitor, and at incubation times longer than 2 h, pathophysiological concentrations induced significant effects. Treatment of MCF-7 cells with the aldehydes caused similar losses of pyruvate kinase activity to those observed in vitro, and at lower concentrations than those required to cause cell death, with time and dose-dependent effects; acrolein adducts on Cys152 and Cys358 were detected. Cys358 and Cys474 are located at or near the allosteric or active sites, and formation of adducts on these residues probably contributes to loss of activity at low treatment concentrations. This study provides the first detailed analysis of the structure-activity relationship of C3 and C6 aldehydes with pyruvate kinase, and suggests that reactive short-chain aldehydes generated in diseases with an oxidative aetiology or from environmental exposure such as smoking could be involved in the metabolic alterations observed in cancer cells, through alteration of pyruvate kinase activity.
Tailoring small molecules for an allosteric site on procaspase-6.
Murray Jeremy,Giannetti Anthony M,Steffek Micah,Gibbons Paul,Hearn Brian R,Cohen Frederick,Tam Christine,Pozniak Christine,Bravo Brandon,Lewcock Joe,Jaishankar Priyadarshini,Ly Cuong Q,Zhao Xianrui,Tang Yinyan,Chugha Preeti,Arkin Michelle R,Flygare John,Renslo Adam R
Although they represent attractive therapeutic targets, caspases have so far proven recalcitrant to the development of drugs targeting the active site. Allosteric modulation of caspase activity is an alternate strategy that potentially avoids the need for anionic and electrophilic functionality present in most active-site inhibitors. Caspase-6 has been implicated in neurodegenerative disease, including Huntington's and Alzheimer's diseases. Herein we describe a fragment-based lead discovery effort focused on caspase-6 in its active and zymogen forms. Fragments were identified for procaspase-6 using surface plasmon resonance methods and subsequently shown by X-ray crystallography to bind a putative allosteric site at the dimer interface. A fragment-merging strategy was employed to produce nanomolar-affinity ligands that contact residues in the L2 loop at the dimer interface, significantly stabilizing procaspase-6. Because rearrangement of the L2 loop is required for caspase-6 activation, our results suggest a strategy for the allosteric control of caspase activation with drug-like small molecules.
Benserazide, the first allosteric inhibitor of Coxsackievirus B3 3C protease.
Kim Bo-Kyoung,Cho Joong-Heui,Jeong Pyeonghwa,Lee Youngjin,Lim Jia Jia,Park Kyoung Ryoung,Eom Soo Hyun,Kim Yong-Chul
Coxsackievirus B3 is the main cause of human viral myocarditis and cardiomyopathy. Virally encoded Coxsackievirus 3C protease (3C(pro)) plays an essential role in viral proliferation. Here, benserazide was discovered as a novel inhibitor from a drug library screen targeting Coxsackievirus 3C(pro) using a FRET-based enzyme assay. Benserazide, whose chemical structure has no electrophilic functional groups, was characterized as a non-competitive inhibitor by enzyme kinetic studies. A molecular docking study with benserazide and its analogs indicated that a novel putative allosteric binding site was involved. Specifically, a 2,3,4-trihydroxybenzyl moiety was determined to be a key pharmacophore for the enzyme's inhibitory activity. We suggest that the putative allosteric binding site may be a novel target for future therapeutic strategies.
Covalent Allosteric Inactivation of Protein Tyrosine Phosphatase 1B (PTP1B) by an Inhibitor-Electrophile Conjugate.
Punthasee Puminan,Laciak Adrian R,Cummings Andrea H,Ruddraraju Kasi Viswanatharaju,Lewis Sarah M,Hillebrand Roman,Singh Harkewal,Tanner John J,Gates Kent S
Protein tyrosine phosphatase 1B (PTP1B) is a validated drug target, but it has proven difficult to develop medicinally useful, reversible inhibitors of this enzyme. Here we explored covalent strategies for the inactivation of PTP1B using a conjugate composed of an active site-directed 5-aryl-1,2,5-thiadiazolidin-3-one 1,1-dioxide inhibitor connected via a short linker to an electrophilic α-bromoacetamide moiety. Inhibitor-electrophile conjugate 5a caused time-dependent loss of PTP1B activity consistent with a covalent inactivation mechanism. The inactivation occurred with a second-order rate constant of (1.7 ± 0.3) × 10 M min. Mass spectrometric analysis of the inactivated enzyme indicated that the primary site of modification was C121, a residue distant from the active site. Previous work provided evidence that covalent modification of the allosteric residue C121 can cause inactivation of PTP1B [Hansen, S. K., Cancilla, M. T., Shiau, T. P., Kung, J., Chen, T., and Erlanson, D. A. (2005) Biochemistry 44, 7704-7712]. Overall, our results are consistent with an unusual enzyme inactivation process in which noncovalent binding of the inhibitor-electrophile conjugate to the active site of PTP1B protects the nucleophilic catalytic C215 residue from covalent modification, thus allowing inactivation of the enzyme via selective modification of allosteric residue C121.
Taxodione and arenarone inhibit farnesyl diphosphate synthase by binding to the isopentenyl diphosphate site.
Liu Yi-Liang,Lindert Steffen,Zhu Wei,Wang Ke,McCammon J Andrew,Oldfield Eric
Proceedings of the National Academy of Sciences of the United States of America
We used in silico methods to screen a library of 1,013 compounds for possible binding to the allosteric site in farnesyl diphosphate synthase (FPPS). Two of the 50 predicted hits had activity against either human FPPS (HsFPPS) or Trypanosoma brucei FPPS (TbFPPS), the most active being the quinone methide celastrol (IC50 versus TbFPPS ∼ 20 µM). Two rounds of similarity searching and activity testing then resulted in three leads that were active against HsFPPS with IC50 values in the range of ∼ 1-3 µM (as compared with ∼ 0.5 µM for the bisphosphonate inhibitor, zoledronate). The three leads were the quinone methides taxodone and taxodione and the quinone arenarone, compounds with known antibacterial and/or antitumor activity. We then obtained X-ray crystal structures of HsFPPS with taxodione+zoledronate, arenarone+zoledronate, and taxodione alone. In the zoledronate-containing structures, taxodione and arenarone bound solely to the homoallylic (isopentenyl diphosphate, IPP) site, not to the allosteric site, whereas zoledronate bound via Mg(2+) to the same site as seen in other bisphosphonate-containing structures. In the taxodione-alone structure, one taxodione bound to the same site as seen in the taxodione+zoledronate structure, but the second located to a more surface-exposed site. In differential scanning calorimetry experiments, taxodione and arenarone broadened the native-to-unfolded thermal transition (Tm), quite different to the large increases in ΔTm seen with biphosphonate inhibitors. The results identify new classes of FPPS inhibitors, diterpenoids and sesquiterpenoids, that bind to the IPP site and may be of interest as anticancer and antiinfective drug leads.
Celastrol Promotes Weight Loss in Diet-Induced Obesity by Inhibiting the Protein Tyrosine Phosphatases PTP1B and TCPTP in the Hypothalamus.
Kyriakou Eleni,Schmidt Stefanie,Dodd Garron T,Pfuhlmann Katrin,Simonds Stephanie E,Lenhart Dominik,Geerlof Arie,Schriever Sonja C,De Angelis Meri,Schramm Karl-Werner,Plettenburg Oliver,Cowley Michael A,Tiganis Tony,Tschöp Matthias H,Pfluger Paul T,Sattler Michael,Messias Ana C
Journal of medicinal chemistry
Celastrol is a natural pentacyclic triterpene used in traditional Chinese medicine with significant weight-lowering effects. Celastrol-administered mice at 100 μg/kg decrease food consumption and body weight via a leptin-dependent mechanism, yet its molecular targets in this pathway remain elusive. Here, we demonstrate in vivo that celastrol-induced weight loss is largely mediated by the inhibition of leptin negative regulators protein tyrosine phosphatase (PTP) 1B (PTP1B) and T-cell PTP (TCPTP) in the arcuate nucleus (ARC) of the hypothalamus. We show in vitro that celastrol binds reversibly and inhibits noncompetitively PTP1B and TCPTP. NMR data map the binding site to an allosteric site in the catalytic domain that is in proximity of the active site. By using a panel of PTPs implicated in hypothalamic leptin signaling, we show that celastrol additionally inhibited PTEN and SHP2 but had no activity toward other phosphatases of the PTP family. These results suggest that PTP1B and TCPTP in the ARC are essential for celastrol's weight lowering effects in adult obese mice.